Process of insolubilizing protein fibers during their manufacture



Patented Sept. 29,1942

OFFICE PRQCESS F INSOLUBILIZING PROTEIN. FI- MANUFACTUBE arms nuamd rumAntonio Ferretti, Milan,

Italy; vested in the Allen todian Property Gus in Drawing.ApplicationMaroh 2, 1940.

- No. 321,9 18.- in Italy March so, 1039 Serial scams. (or. 18-54) Theobject of the present invention is a process .for insolubilizing proteinfibers, during their manufacture and the fibers obtained by saidprocess.

(1 Propositions have been already known for insolubilizing relatively towater, artificial fibers of proteins by submitting them to the actionof,

chrome salts in aqueous solutions; in particular Mr. A. Millar in hisEnglish Patent No. 6,700 A. D. 1898 has proposed to render proteinfibers insoluble in water by treating them with a watery solution of 5%of chrome-alum or of bichromate of potash; but these suggestions for'insolubilization have not found a practical achievement, because-beforemy patent application No. 06,470 filed in U. S. of America on August 17,1936- nobody had yet succeeded in making fibers solely of protein andtherefore the product to be submitted actually-and not only on papertothe action of chrome salts in aqueous solution had yet to be obtainedfor ascertaining. really the insolubilizing effects of the chrome salts.

Therefore, Miller and other researchers, have not even been able tonotice that protein fibers cannot be treated in watery solutionscontaining solely chrome salts, due to the fact that the filamentsfreshly coagulated, namely not yet insolu- In fact "Galalith" isrendered insoluble by dipping it in watery baths of formaldehyde, butthis bilized, do swell enormously in said watery solution anddeteriorate in an incurable manner, before the chrome salts can performtheir insolubilizing action upon said filaments; in fact protein fibersthus treated lose entirely their tensile resistance, are brittle andtherefore useless for textile uses. A

(2) In my preceding patent applications (No. 96,470 filed in U. S. ofAmerica on August 17, 1936 and No. 191,000 filed in U. S. of America onFebruary 1'7, 1938) I have proved already that also the treatment ofprotein filaments with formic aldehyde cannot be carried out in waterysolutions of only formic aldehyde, because also in such a case thefilaments deteriorate completely before their insolubilization.

In fact, the few researchers, who, before my patents, have uselesslytried to succeed in producing protein fibers, failed in their attempts,not only due to the many errors committed in the other various stages ofthe process, but also because in the stage of insolubilization they allerroneously thought, that it would be simply sumcient to dip the freshlycoagulated filaments in a watery solution of' formic aldehyde; 'theytried simply to apply'to protein fibers the already known method forinsolubilizing the so-called product is formed by paracasein, which,among other features, is not soluble in alkalis and is aplasticmaterial, which on being pressed invarious dies, is neutral andcontains only a small percentage of moisture (20%); therefore it issufficiently solid after coming out of the press to re main withoutalterations within a watery solution of formaldehyde. I

Casein on the contrary, differently from paracasein, is no plasticmaterial; it must be dissolved in alkali and water and reaches thespinnerets in a solution in which, for each hundred parts of casein,there are about five hundred parts of water; therefore the caseinfilaments, freshly coagulated, contain yet three hundred parts of water,acid and salts for each hundred parts of casein and said filaments insuch a condition are so delicate that the slightest disturbance destroysthem completely.

These filaments, when dipped in a watery solution of formaldehyde, swellenormously even to practical dissolution, before the formaldehyde mayhave time to achieve the insolubilization, which then takes place whenthe filaments are already completely destroyed.

This action occurs, without taking into account the destructive actionof the high percentage of acid present in the filaments during theinsolubilizing process, which percentage should be reduced or eliminatedwith a washing treatment which cannot be applied, as the filaments wouldimmediately dissolve'in the water.

In my preceding patents, above recited, this main phase has been solvedscientifically and practically: As soon as they have coagulatednamelybefore being destroyed by the presence of -a high percentage of acid-thefilaments pass into a first bath of sodium chloride, wherein they getrid of the excess of acid, without any further swelling, that is, theykeepin the state of swelling they had reached at the time of theircoagulation; immediately afterwardsthey pass through a second bath ofaluminium salts and of sodium chloride, with or without formaldehyde,wherein the filaments are restrained and preliminarily hardened by theastringent action of aluminium salts, this action being helped-on andaccelerated "Ga1alith in watery solutions of formaldehyde.

by the presence of the sodium chloride, which controls also theastringent action of the aluminium salts, actingnamely as a control ofthe. swelling for allowing the aluminium salts to penetrate also theinnermost partsof the filaments; without said action .only a superficialouter hardening would be obtained which would render brittle the fibersafter their desiccation. As this point comes in the third bath composedof formaldehyde, aluminium salts and sodium chloride, namely when thefilaments, freed from the excess of acid and gone back in their swellingwithout their being damaged, are ready to be subjected to theinsolubilizing action of formaldehyde in a bath wherein the presence ofthe salts of aluminium and of sodium chloride plays the very importantpart of keeping the filaments in that slight swollen condition requiredfor obtaining a quick and perfect insolubilization.

Of course the freshly coagulated filaments could be insolubilizeddirectly in the third bath stated above, omitting the first and secondbaths, as the astringent action of the aluminium salts and theregulating action of sodium chloride are instantaneous and therefore theinsolubilizing process with formaldehyde can begin regularly andimmediately; but this would rapidly soil the baths with acid, whichwould require frequent neutralizations of a rather expensive bath,whilst, on eliminating instead the excess of acid by means of sodiumchloride, the cost is very slight, due to the cheap salt, whose presenceis on the other hand so important in the subsequent treatment ofinsolubilization, and it is therefore convenient to predispose it intothe filaments utilizing the first treatment of elimination of the acidby a solution of sodium chloride.

From the above statements it is apparent that the insolubilization ofcasein fibers is not so simple an operation as thought by theresearchers who have attempted in vain the manufacture of proteinfibers.

Now I have discovered that the same basic principles reviewed above,should be applied to the protein fibers even when insolubilizing withchrome salts, in order to avoid the deterioration of the fibers, so asto obtain a final product useful in textile industries.

(3) Other researchers have found lately that casein fibers manufacturedaccording to my patents and already insolubilized with formaldehyde, maybe subsequently treated with the aqueous solutions of chrome-salts,already mentioned under Paragraph (1) above, thus avoiding thedeterioration of the fibers which takes place when that same treatmentis applied to fibers of freshly coagulated casein, viz., not first,insolubilized with formic aldehyde.

And not this only, but said chrome treatment applied to fibers whichhave been precedingly insolubilized with formic aldehyde, greatlyimproves the resistance of the same fibers to the action of dyes inboiling acid baths; it allows also the obtaining of more solid coloursboth with dyes in acid as with chrome dyes, and in general an increaseof the resistance of the fibers to the action of alkalis or otherchemical or physical agents.

Truly chrome treated casein fibers lose their whiteness and take up agreenish blue hue, so that they cannot take up light colours, but theusefulness of the chrome treatment remains very important even whenlimited to the gamut of dark hues.

The achievement of such good results depends on the fact-that the caseinfibers already insolubilized with formic aldehyde and preferably alreadydried, when dipped subsequently in the watery solution of chromiumsalts, swell only slightly and in a measure required for allowing thesalts of chrome to penetrate intimately within the fibers, whereupon theoxide of chrome fixes without damaging them.

All this confirms fully the facts stated in Paragraphs (1) and (2)above.

(4) Therefore the present invention does not concern the treatment withchrome salts of protein fibers which have been precedingly insolubilizedwith formic aldehyde and other chemicals, but the solving of the wholeproblem of treating with chrome salts the protein fibers during theirmanufacture, namely precedingly or simultaneously to theirinsolubilization with formic aldehyde, butavoiding any damaging of thefilaments, which acquire therefore all the properties obtaining from thetreatment with chrome salts achieved after their insolubilization withformic aldehyde as stated above in Paragraph Thus the aim is reachedwith a great saving in labor, in ener y, in steam and processing plantetc. inasmuch as the application of the treatment during the manufactureof the fibers is achieved without requiring any extra expense,

barring the final neutralizing process.

(5) I propose therefore that the chrome treatment of the proteinfilaments freshly coagulated. should be made in waterysolutions-containing not only chrome salts, but also one or more solublesalts, preferably neutral or acid, as for instance: chlorides,sulphates, acetates, formiates, etc. and among all these, preferablysodium chloride and aluminium sulphate.

This being so stated and disclosed, the practice of the presentinvention may be carried-on in the following ways.

(A) It is unadvisable to add salts of chrome to the coagulating bathcontaining sulphuric acid, sodium sulphate or other salts, as in thewashing of the fibers which follows immediately, there would result ahigh loss of non-fixed chrome salts; further it is preferable to avoidthe chrome treatment in the presence of a high percentage GramsAluminium sulphate per liter of bath; 180-200 Sodium chloride 150-160 Insuch a bath may be added the soluble basic chrome salts, preferablychrome sulphate in the proportion of 50 gr. per liter of bath, inreplacement of 50 gr. of aluminium sulphate.

Having chrome salts in this bath, the content of aluminium sulphate init may be further reduced, replacing it with further sulphate ofchromium, but this would increase uselessly the production cost,therefore it is preferable to replace it with a greater amount of sodiumchloride when the bath should be so modified.

One can also entirely replace in this bath the aluminium sulphate,increasing to -150 gr. per liter the chrome sulphate and increasing alsothe amount of sodium chloride, which would be preferably present in thebath in a quantity greater than that of chrome sulphate; in such a case,however, the bath has less astringent power on the filaments, due to thelack'of aluminium sulphate, and therefore this modification is not to bepreferred also because it increases the cost of production.-

The temperature of these baths should be higher than 25 (3., preferably55-65 C.

(D) Instead of adding the salts of chrome to the bath as stated under(C) above, they may be added in the bath collecting the freshly cutfibers, which bath may be ofthe following composition:

Grams Aluminium sulphate per liter of bath.. 130-140 Sodium chloride perliter of bath 140-150 Chrome sulphate per liter of bath 50- 60 This bathshould have a'temperature maintained above 25 0., preferably 35-40 C.for one hour, rising thereafter to 60-70". C. and maintained so for 6 to9 hours.

(E) Should it be desired to associate the chrome treatment with theformic aldehyde, the latter may be added in any of the above statedbaths,

preferably in the proportion of 40 gr. of 100% formic aldehyde per literof bath.

(F) It should be noted that the best results in the quality of theprotein fibers are achieved by carrying-on the insolubilizationsimultaneously with chrome and with formic aldehyde, and therefore thesimplest and cheapest method for achieving said results is that oftreating the fibers in a vacuum boiler in the last insolubilizing bath,composed for instance as follows: 1

. Grams Aluminium sulphate per liter of bath 40- 50 Chrome sulphate perliter of bath 50- 60 Sodium chloride per liter of bath .4 180-200 Formicaldehyde 100% per liter of bath .40

- Temperature of the bath above 25 C. preferably at 70 0 for 6 to 9hours.

In this case the protein fibers are manufactured without any change inregard to what was stated in my preceding patents quoted above, andthisright down to the last but one stage of the process, while in thelast stage the chrome salts are added to the insolubilizing bath so asto obtain the composition given above by way of example.

The chrome-treated fibers, besides requiring ample subsequent washing,should be neutralized ferred example, but I can use also chrome alum,

chrome chloride and other salts capable of providing solutions ofchromeoxide or tanning compounds containing chrome salts; the basicfeature of the solutions of chrome oxide may be supplemented by anyknown means without thereby exceeding the limits of the presentinvention.

Having now particularly described and ascertained the nature of my saidinvention and in what manner the same is to be performed, I declare thatwhat I claim is:

1. In a process for the commercial production of artificial textilefibers from a viscous maturated alkaline protein solution, and followingthe step ,of multiple spinning thereof with acid coagulation of thefilaments; the step of then insolubilizlng the freshly coagulatedacid-containing group of spun filaments, namely, by'subjecting thempromptly to treatment in an aqueous insolubilizing bath which contains asoluble chrome compound, which has an effective insolubilizing actionupon the soft protein filaments, taken from the group consisting ofchrome sulfate, chloride and alum; and of sodium chloride acting torestrain swelling of filaments during insplubilizing. v

2. In a process for the commercial production of artificial textilefibers from a. viscous maturated alkaline casein solution, and followingthe step of multiple spinning thereof with acid coagulation of thefilaments; the step of nextv insolubilizing the freshly coagulatedacid-containing grou of spun filaments by subjecting them to treatmentin an aqueous insolubilizing bath which contains a soluble chromecompound which is a basic salt, of the group consisting of thesulphates, chlorides and alums, and has an effective insolubilizingaction on the soft protein filaments, together with a proportion ofsodium chloride for controlling the insolubilization, and aluminumsulphate for hardening them.

3. A process as in claim 2 and wherein with the insolubilizing chromecompound is included in the bath a proportion of formaldehyde forinsolubilizing. 1

4. In a process for the commercial production of artificial textilefibers from a viscous maturated alkaline casein solution, whichcomprises spinning such casein solution into filaments and coagulatingsuch filaments in an acid coagulating bath; insolubilizing the freshlycoagulated filaments after leaving said bath; by subjecting them totreatment in an aqueous insolubilizing bath which contains a chromesulphate, sodium chloride, and aluminum sulphate.

5. In a process for the commercial production of artificial textilefibers from a viscous maturated alkaline casein solution, whichcomprises spinning such casein solution into filaments and coagulatingsuch filaments in an .acid coagulating bath; insolubilizing the freshlycoagulated filaments after leaving said bath; bysubjecting them totreatment an aqueous insolubilizing bath which contains a chromesulphate, sodium chloride, and formaldehyde. 6. A process as in claim 5and wherein the bath contains aluminuin sulphate.

ANTONIO mam.

